The present invention pertains to the technical field of motor cooling devices.
One method of driving electric automobiles that has been proposed is the in-wheel drive system, in which a motor is installed in each wheel. The characteristic features of this in-wheel drive system include an increase in the usable cabin space and independently driven wheels so that a different driving sensation than that of conventional automobiles can be produced.
In order to realize such a drive system, the size of the motor may be made smaller. But as the size of the motor decreases, so too does the area for dissipating the generated heat; thus, the temperature rises significantly.
Cooling systems include liquid-cooling systems and air-cooling systems. In the liquid cooling system, although a higher cooling efficiency can be expected, it is may be necessary to use a pump or another circulating device, as well as conduits for circulating the coolant to the motor installed in each wheel. In this case, a heat exchanger for the coolant is placed near the front grille, and since long conduits may be needed to connect the heat exchanger to the motors, the overall size of the cooling system becomes larger.
A sealed electric compressor has also been proposed in Japanese Kokai Patent Application No. 2001-12352(page 3, FIG. 2), which has a water circulating tube wound on the outer wall of the motor housing, and, in this case, the pump for circulating the coolant is integrally assembled.
It would be desirable to provide a motor cooling device that is smaller and lighter in weight.